Increasing Accessible Active Site Density of Non-Precious Metal Oxygen Reduction Reaction Catalysts through Ionic Liquid Modification

Employing a Zn-air/Photo-Electrochemical Cell for In Situ Generation of H2O2 for Onsite Control of Pollutants

Industrial production of hydrogen peroxide (H2O2) is energy-intensive and generates unwanted byproducts. Herein, an alternative production strategies of H2O2 are demonstrated in a Zn-air and a photoelectrochemical cell. Employing an optimally produced reduced graphene oxide (rGO) electrocatalyst@air-cathode, an impressive power density of 320 Wmgeo -2 (geo = geometric area) is achieved along with a high H2O2 production rate of 3.17 mol mgeo -2h-1 (operating potential = 0.8 V). Systematic investigations reveal the critical role of specific functional groups (viz. C─O─C, chemisorbed O2, C≐C) to be responsible for enhancing the yield of H2O2. The in situ generated superoxide (O2˙) and hydroxyl radicals (˙OH) act as oxidants to efficiently degrade onsite, a model textile dye pollutant (viz. rhodamine B) inside the Zn-air cell. Using the identical rGO as the photoelectrode in an H-type cell, the H2O2 production is remarkably enhanced under visible light illumination. Simultaneously, the onsite pollutant degradation occurs five times faster than the Zn-air cell (at the same operating potential = 0.8 V). This work opens a new paradigm for electrosynthesis, wherein an underlying redox can be utilized to synthesize industrial chemicals for onsite control of environmental pollution sustainably.

Surface engineering for stable electrocatalysis

In recent decades, significant progress has been achieved in rational developments of electrocatalysts through constructing novel atomistic structures and modulating catalytic surface topography, realizing substantial enhancement in electrocatalytic activities. Numerous advanced catalysts were developed for electrochemical energy conversion, exhibiting low overpotential, high intrinsic activity, and selectivity. Yet, maintaining the high catalytic performance under working conditions with high polarization and vigorous microkinetics that induce intensive degradation of surface nanostructures presents a significant challenge for commercial applications. Recently, advanced operando and computational techniques have provided comprehensive mechanistic insights into the degradation of surficial functional structures. Additionally, various innovative strategies have been devised and proven effective in sustaining electrocatalytic activity under harsh operating conditions. This review aims to discuss the most recent understanding of the degradation microkinetics of catalysts across an entire range of anodic to cathodic polarizations, encompassing processes such as oxygen evolution and reduction, hydrogen reduction, and carbon dioxide reduction. Subsequently, innovative strategies adopted to stabilize the materials' structure and activity are highlighted with an in-depth discussion of the underlying rationale. Finally, we present conclusions and perspectives regarding future research and development. By identifying the research gaps, this review aims to inspire further exploration of surface degradation mechanisms and rational design of durable electrocatalysts, ultimately contributing to the large-scale utilization of electroconversion technologies.

Enhancing Polymer Electrolyte Membrane Fuel Cells with Ionic Liquids: A Review

Polymer electrolyte membrane fuel cells (PEMFCs) represent a promising clean energy solution. However, their widespread adoption faces hurdles related to component optimization. This review explores the pivotal role of ionic liquids (ILs) in enhancing PEMFC performance, focusing on their role in polymer electrolyte membranes, catalyst modification, and other components. By addressing key obstacles, including proton conductivity, catalyst stability, and fuel crossover, ILs provide a pathway towards the widespread commercialization of PEMFCs. In the realm of PEMFC membranes, ILs have shown great potential in improving proton conductivity, mechanical strength, and thermal stability. Additionally, the utilization of ILs as catalyst modifiers has shown promise in enhancing the electrocatalytic activity of electrodes by serving as an effective stabilizer to promote the dispersion of metal nanoparticles, and reduce their agglomeration, thereby augmenting catalytic performance. Furthermore, ILs can be tailored to optimize the catalyst-support interaction, ultimately enhancing the overall fuel cell efficiency. Their unique properties, such as high oxygen solubility and low volatility, offer advantages in terms of reducing mass transport and water management issues. This review not only underscores the promising advancements achieved thus far but also outlines the challenges that must be addressed to unlock the full potential of ILs in PEMFC technology, offering a valuable resource for researchers and engineers working toward the realization of efficient and durable PEMFCs.